A microstructural study of low resistivity tin-doped indium oxide prepared by d.c. magnetron sputtering

The microstructure of low resistivity (∼ 2 × 10−4 Ω cm) Sn-doped In2O3 (ITO) thin films prepared by multipass d.c. magnetron sputter deposition with an ITO (10 wt.% SnO2) target onto soda-lime glass substrates was investigated using plan-view and cross-sectional transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction. Each pass of the multipass sputter process deposits a 110 nm thick ITO layer. The substrate temperature was 400 °C during deposition and the sputter chamber was back-filled to a pressure of 1 × 10−3 Torr with a mixture of Ar and 0.8–1.0 at.% O2. Plan-view TEM studies combined with SEM observations of the film surface reveal that the sputtered ITO possesses a polycrystalline structure in which 200–350 nm grains are subdivided into highly oriented regions 10–30 nm in diameter. X-ray diffractometry studies show that the as-deposited films have a strong 〈100〉 texture and cross-sectional TEM studies reveal prominent columnar growth in the through-thickness direction.